Fix duplicate copilot-preflight step ID when threat detection is enabled

[Copilot]

When threat detection is enabled on a Copilot workflow, the compiler emits both a main execution step and a detection execution step into the same job scope — both with id: copilot-preflight — causing GitHub Actions to reject the compiled workflow.

Changes

• pkg/workflow/threat_detection.go: buildDetectionEngineExecutionStep already prefixed agentic_execution → detection_agentic_execution to avoid ID collisions; extends the same logic to rename copilot-preflight → detection-copilot-preflight

prefixed := strings.Replace(line, "id: agentic_execution", "id: detection_agentic_execution", 1)
prefixed = strings.Replace(prefixed, "id: copilot-preflight", "id: detection-copilot-preflight", 1)

• Recompiled workflows: release.lock.yml (and all other affected lock files) now emit distinct step IDs — copilot-preflight for the main step, detection-copilot-preflight for the detection step.

[pelikhan]

@copilot do not emit copilot-preflight twice.